<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>DOM 事件模型 event model</title>
</head>
<body>
    <boutton id="btn1" onclick="hander1(this.innerHTML)">按钮1</boutton>
    <boutton id="btn2">按钮2</boutton>
    <boutton id="btn3">按钮3</boutton>
    <boutton id="btn4">按钮4</boutton>
    <script>
        function hander1(content){
            console.log(content);
        }

        //model 2
        const btn2 = document.getElementById('btn2');
        btn2.onclick = 
    </script>
</body>
</html>